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Name: Jane 
Status: student
Grade: 9-12
Country: Canada
Date: March 2009


Question:
Does the meniscus of water against a solid surface vary with the make up of the solid? If so, how does it vary?


Replies:
Hi Jane,

Yes, the meniscus of water varies considerably depending on the material it is in contact with. The more hydrophobic the material is, the less the meniscus rises. The lower a material's inherent surface energy, the more hydrophobic it is. An extreme example is a material like Teflon that is very hydrophobic (and has very low surface energy). Water in contact with Teflon actually results in a negative meniscus.

Regards,
Bob Wilson


Jane,

It is important to remember that the shape of the meniscus is determined by the *difference* in the strength or type of intermolecular attractive forces of the liquid and the wall of the solid.

If the intermolecular attractive forces are similar then the liquid will tend to adhere more to the solid and the meniscus shape will appear curved facing upward. The attraction to the wall can compete with the attraction of the liquid to itself.

If the solid and liquid have very different intermolecular forces then the meniscus will appear curved facing downward. The liquid's own intermolecular forces will attract the liquid particles inward.

Greg (Roberto Gregorius)


The short answer is yes. However, there is not a short answer. You would need to refer to a specialist text, devoted to surface chemistry/physics. One, but by no means all, the possible texts, is "Principles of Colloid and Surface Chemistry" by Paul C. Hiemenz.

Your question is very large one!

But this is not a "brush off". I commend you for asking a "simple" question with a complex answer. I, for one, just cannot begin to do justice to an adequate answer in a format such as NEWTON.

I do have an action plan for you. Start with "Wikipedia" and/or "Hyperphysics". From either site you will be directed to other sites that address your question in as much detail as you wish to pursue.

Vince Calder



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